Drupal 7 alpha version was released about two months ago.Drupal has released the seventh (and hopefully final) alpha version of Drupal 7.x for your further testing and feedback.
This release includes:
# HUGE number of upgrade path fixes, including automated tests for updates.
# Great usability improvements, including the installer not greeting you with a red error of death anymore on shared hosts!
# Field UI improvements to allow it to be further extended from contrib.
# Numerous Form API fixes and improvements.
# Numerous accessibility fixes.